Fresh Water DHW System Free of Harmful Legionella Bacteria

Flow-through domestic hot water heating ensures the preparation of hot water with the highest hygienic quality. We use large-dimension plate heat exchangers that guarantee the lowest return temperatures to the buffer tank. Our control process adjusts the speed of the high-efficiency charging pump. As a result, only the absolutely necessary amount of electrical energy is used.
Our range of device series covers energy requirements from single-family homes to multi-family buildings, including device cascading.
Circulation mode is available in various configurations. Thanks to the “demand-dependent” operating mode and a temperature sensor at the inlet of the heat exchanger on the potable water side, the shortest operating times can be achieved with maximum efficiency.
In this case, the task of energy storage, instead of a hygienically critical boiler, is handled by a buffer tank filled with heating water, as the heat generator typically cannot deliver the amount and dynamic energy required at the moment of hot water demand.

Advantages of the Fresh Water System

• The buffer stores energy not only for water heating but also for space heating.
• Cycling is eliminated from the heat generator. This refers to sequences of short pauses and low-efficiency operation, comparable to stop-and-go traffic.
• Heat storage tanks are mandatory for solid fuel boilers.
• Upon integrating solar energy, this system structure automatically becomes a solar-assisted heating system.
• Domestic hot water preparation and heating can be operated simultaneously.

This solution provides energy savings, operational safety, and hygiene.

Installation Diagram - Legionella-Free Fresh Water System

VarioFreshNova HE - Fresh Water System

The VARIO fresh-nova heats potable water using a flow-through method. When a hot water tap is opened, the integrated controller detects this via a flow sensor and activates the charging pump at the correct speed in a controlled manner. It pumps water from the tank through a stainless steel plate heat exchanger in the exact amount required for heating to produce hot water.
The hot water temperature can be defined as needed with 6 switching points per working day.
Important information regarding fresh water heating is continuously stored and processed in the controller’s neural network. Thanks to the “machine learning” function, it adapts its behavior to the relevant operating conditions.

DHW Circulation

The integrated circulation pump control supports “on-demand” or “time-dependent” operating modes. Depending on requirements, the circulation pump is activated by briefly drawing hot water (e.g., flushing the tap). A sensor on the circulation return line deactivates it once the desired temperature is reached.
Operating modes can be defined as needed, using 6 switching points per weekday.

1. Mounting Plate

2. Insulated Housing (right side)

3. Insulated Housing (top)

4. Controller

5. Plate Heat Exchanger with Flushing Connections

6. High-Efficiency Charging Pump with Air Vent

7. Flow Sensor

8. Temperature Sensors

9. Piping - with Flat Sealing

10. Circulation - Optional

VarioFresh Nova HE - Performance Table

VARIO fresh-nova HE Cascade ExOpt

The VARIO fresh-nova HE Cascade ExOpt heats potable water using a flow-through method. When cold water flows through the device, the integrated controller detects it via a volumetric flow sensor and activates the charging pump with the appropriate power. It pumps water from the tank through a stainless steel plate heat exchanger in the exact amount required for heating to produce hot water.

VARIO fresh-nova HE Cascade ExOpt - Performance Table

Live Installation - Live Diagram

Characteristics of the Legionella-Free System

The VarioFreshNova domestic hot water heating system is designed by the German company Varmeco, a pioneer of this technology in Europe.

The system is based on flow-through water heating in a stainless steel plate heat exchanger, which draws energy from a heat buffer tank.

The buffer tank is heated via a gas boiler and solar collectors (or other heat sources). This allows maintaining a lower temperature in the tank (50°C) compared to standard systems.

All energy stored in the buffer is used to transfer heat to the DHW plate heat exchanger and, if needed, to central heating, enabling both systems to operate without costly expansion.

The system includes a flow sensor and neural automation that continuously monitors the flow of hot water, stabilizing the outlet water temperature.

It works by maintaining a low flow rate when the first hot water tap is opened, with the charging pump between the buffer and the heat exchanger adjusting its performance to the demand, consuming minimal energy and not depleting the buffer.

As the hot water flow increases due to multiple users, the charging pump boosts performance to meet the demand for domestic hot water. The neural automation ensures a constant outlet water temperature.

This differs significantly from a storage-based system and provides several compelling reasons to adopt this system.

Fresh water system ready for operation

System operates at 20% pump efficiency when drawing hot water from one tap (low pump efficiency – energy savings).

System efficiency increases to 40% when drawing from two taps.

System efficiency at 80% when drawing hot water from all taps (pump efficiency increases).

The system can be expanded into cascades, creating an inexhaustible source of hot water with a capacity of, e.g., 480 l/min (with a cascade of four devices). Cascades can be connected in series to increase capacity, enabling service for the largest facilities.

VarioFreshNova Device Cascade

Frankfurt – Commerzbank Arena

• Design: VARIO fresh-nova
• Capacity: 177/223 l/min
• Tank Version: 2 PS-pur 800/2 PS-pur 1000
• Local Heating
• Hot Water Supply for Players’ Changing Rooms and Catering Area

Fulda Clinic – SYSTEM 018-K2, 3 SYSTEM 018-K3, 4 SYSTEM 018-K4

• Buffer Capacity: 19,000 l
• Capacity: 245 l/min, 5 x 172 l/min, 144 l/min, 115 l/min

Special Heat Storage Systems

Heat or cold storage is more than just a tank. It is the heart of your heating or cooling system. The dimensions and quality of the storage tank determine the efficiency of the entire system.
Due to the significant importance of storage, we have optimized the storage concept. The result: standard and large storage tanks with effective stratification systems ensuring the best possible temperature layering and highly effective insulation for minimal losses.

Rely on the Expertise of Storage Specialists

Varmeco is a professional in hydraulic planning and heat management, while Sirch is a leading company in the heat storage market with fifty years of experience in steel processing.

Our Buffers

• Volumes from 300 to approximately 150,000 liters
• Standard and custom-made products
• Factory-ready or assembledtimized for performance and storage time, we are the right partner for you. You can choose between various standard insulation materials and vacuum insulation (up to 80,000 l) with a lambda value up to 5 times better.
  You can also rely on our expertise for stratification, which enables the use of heat at the appropriate level with minimal reheating or mixing.

   

  Vacutherm Buffers - Nothing Insulates Better Than a Vacuum

  Conventional insulation materials have their limitations: doubling the insulation layer does not halve heat losses.
  Therefore, we offer our Vacutherm tanks for particularly high requirements and compact dimensions. They feature a long-term stable vacuum between the inner and outer walls. Thanks to minimal losses, heat stored in a solar system during the summer can still be used on cool autumn days. Additionally, it increases the comfort of indoor installations, as the building is not heated by the tank.

  Food Industry - SYSTEM 018 K2 - Capacity 120 l/min, Buffer Capacity 30,000 l

  

  Swimming Pool - SYSTEM 018-K2, SYSTEM 018-K4

  Capacity: 94 l/min, 168 l/min

  Buffer Capacity: 3,000 l

  

  

  

  Campsite - SYSTEM 019-K4

  Capacity: 330 l/min

  Buffer Capacity: 9,000 l

  Solar Collector: 100 m²

  

  

  

  Multi-Family Buildings - 2 x SYSTEM 018-K2, 2 x SYSTEM 018 EDITION

  

  

  

  Safety

  In storage-based domestic hot water tanks, pathogenic bacteria thrive ideally at 35-40°C. All tap water contains Legionella bacteria, which multiply at temperatures from 25-55°C (ideally 35-40°C).

  At 40°C, the number of bacteria doubles within 2 hours. The longer the water remains at this temperature, the greater the risk of an exponential bacterial growth, endangering users with infection. A 20-hour exposure at this temperature increases the count from 1 CFU/liter to 1,000 CFU/liter.

  Infection occurs through droplet inhalation during showering.

  Legionella causes severe pneumonia, resulting in 20-30% mortality.

  PHARMIND, a German medical journal, reports that 13.6% of 110 pneumonia cases are caused by Legionella infection.

  A less harmful infection, known as Pontiac fever, causes flu-like symptoms and is also triggered by the same bacteria.

  To prevent this, the tank temperature must be raised to 70°C once a week, typical for storage-based systems.

  However, thermal disinfection causes specific issues:

  • Heating water to 70°C increases energy consumption,
  • It causes the formation of hard-to-remove limescale,
  • It increases energy use due to reduced thermal conductivity from limescale,
  • It provides a breeding ground for Legionella bacteria,
  • It causes corrosion.

  Storage-based water heating systems above 400 liters must be operated at 60°C for hygienic reasons, leading to energy losses due to more frequent gas boiler activation, standby losses, and circulation-related losses.

  Energy Losses and Savings

  In the VarioFreshNova system, hot water is heated on-demand, calculated by the previously described neural automation.

  This solution allows heating water in the tank to just 50°C, resulting in significant savings.

  Any DHW installation with sections longer than 3 meters between the water heating source and the draw-off point must, by law, be equipped with circulation. The higher the water temperature in the tank, the larger the circulation pumps required and the more frequent the circulation.

  Energy losses in a 60°C water heating system are one-third higher than at 45°C.

  Additionally, the supply temperature to the boiler’s coil is higher at 60°C (especially in summer, when it cannot be used for heating), increasing flue gas temperatures and resulting in energy losses of up to 14%.

  Standby losses are also one-third higher in a 60°C system compared to 45°C.

  System Comparison - Fresh Water vs. Storage-Based

  Losses / Savings	Storage-Based System - Boilers	Flow-Through System with VarioFreshNova Buffer
  Outlet Water Temperature	60°C	50°C	60°C
  Standby Losses	4.00%	3.00%	4.00%
  Losses from Hot Water Heating and Circulation	30.0%	22.50%	30.00%
  Boiler Standby Losses	4.00%	1.00%	1.00%
  Boiler Flue Losses	14.00%	1.00%	1.00%
  Total	44.90%	26.30%	34.10%
  Energy Demand - Fuel for 1,000 kWh of Hot Water – Useful Heat in kWh	1,815	1,357	1,518
  Savings %	-	-25%	-16%

   

  Table 1. System Comparison

  Varmeco Solar BackPack - Renewable Energy Sources

  

  

  Figure 9. Renewable Energy Sources - Cooperation with Solar Collectors

  The VarioFreshNova system works perfectly with renewable energy sources.

  Domestic hot water can be supported by solar collectors even at lower temperatures (e.g., 50°C). This results in significant savings during winter, early spring, and autumn, when sunny days are scarce. The VarioFreshNova system enables full utilization of solar collectors, reducing operating costs.

  Hot water can also be heated using ground-source heat pumps as the primary heat source. A heat pump draws heat from the ground and is a renewable energy source, 30% cheaper than natural gas for DHW heating alone.

  Both heat pumps and gas boilers in the VarioFreshNova system can serve as heat sources for both heating, modernizing old central heating systems, and DHW production.

  Solar Collectors

  

  

  

  

  VARIOcollect E Solar Collector

  The system can be expanded with large-format flat-plate collectors.

  The collectors have a surface area ranging from 2.5 to 24 m² and can be installed on roofs or building facades (Figure 10).

  The size of individual elements (width: 2,015–7,955 mm, height: 1,250–3,000 mm) allows for quick installation.

  Increasing the collector surface reduces losses through the collector frame and increases efficiency.

  Thanks to flexible supply and return connections, the collector supports customized piping, and its large dimensions minimize the number of pipes, reducing pressure losses.

  The entire system is covered with a safe, prismatic, high-transparency, low-iron glass with 91% transparency and low reflectivity.

  The collector frame can be made of aluminum profiles, titanium-zinc, copper, stainless steel, Uginox-special galvanized steel, or lead glass, all in a screwless system.

  Collector connections can be made with copper or stainless steel pipes.

  VARIO PS pur KX Buffer Tank

  

  VARIO PS pur KX Buffer Tank - Stratification - TANK LOADING AND UNLOADING

  Vario PS-pur KX tanks are precisely manufactured from high-quality materials. The shell is made of layered steel sheet grade S235JRG2 (St 37-2) with a thickness of 3 mm.

  The tank is equipped with twelve connections:

  • Four supply nozzles equipped with deflectors for tank stratification,
  • Four return nozzles,
  • A charging and discharging nozzle for efficient heat utilization from the tank,
  • A temperature measurement nozzle,
  • One sealed nozzle,
  • A stratification channel.

  The position of the nozzles is always individually designed.

  The system cooperating with a solar installation is equipped with an internal smooth-tube coil with a surface area of 1.5 m²–3 m².

  Tanks are available in sizes: 550, 800, 1,000, 1,500, 2,000, 3,000, 5,000 liters.

  For special applications, up to 24 m³.

  These sizes are flexible and can be configured based on needs, e.g., number of nozzles, connection type and diameter, tank equipment with a heat exchanger, stratification deflectors, and working pressure of 6, 10, or 16 bar.

  The tank insulation is made of 100 mm thick soft PUR foam.

  NOVAtron Cogeneration - Electricity and Heat from Gas!

  

  NOVAtron Cogeneration

  The unit is an optional solution supporting the supply of buildings with electricity and combined energy—heat stored in a buffer tank.

  The unit modulates in the power range of 5–20 kW electrical and 12–43 kW thermal.

  The NOVAtron cogeneration unit, generating electricity with heat recovery, is powered by natural gas, liquid gas, or pure biogas.

  The heart of the unit is an electronically controlled industrial 4-cylinder Volkswagen engine with a 2.0-liter capacity, water-cooled, with an asynchronous decoupled generator operating in dual mode (grid and generator), easy to operate, and controlled by highly intelligent automation (3x400 V, 22 kW/40 A).

  The engine features an automatic oil change function!

  Heat is recovered by a built-in plate heat exchanger and transferred to a buffer tank in a system like VARIO fresh nova (flow rate 1.8 m³/h at Δt=20K, pressure loss 0.4 bar).

  System components ensure the highest quality of operation and user-friendliness:

  • Clutch,
  • Crankshaft housing ventilation reducing oil consumption and emissions,
  • Gas path regulation,
  • Primary cooling circuit,
  • Highly advanced safety system.

  Unit operation and control are also available remotely via a publicly accessible network.

  Innovative technology:

  • Highly sensitive mixture regulation for balanced fuel consumption reduction,
  • Oil recovery during crankshaft ventilation using the AirClean method,
  • Fast-reacting and highly responsive to energy demand.

  Advantages:

  • Smooth three-phase start,
  • Vibration-free engine and generator connection,
  • Double lifespan of the generator shaft,
  • CANBus - Engine electronics communication for power and emissions optimization,
  • Highest mechanical and thermal durability of exhaust-contact components due to certified components with excellent chemical and marine atmosphere resistance,
  • Optimal operational safety thanks to dual ventilation technology in the gas path,
  • Component connections with vibration and temperature protection via automotive-standard wiring (MIL, UL, CSA, DIN, EN, EIA-TIA),
  • Low noise level <50 dBA,
  • Fully automatic oil change.